tcp: annotate tp->snd_nxt lockless reads

There are few places where we fetch tp->snd_nxt while
this field can change from IRQ or other cpu.

We need to add READ_ONCE() annotations, and also make
sure write sides use corresponding WRITE_ONCE() to avoid
store-tearing.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 339944690329..c802bc80c400 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -482,8 +482,10 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
         WRITE_ONCE(newtp->rcv_nxt, seq);
         newtp->segs_in = 1;
 
-        newtp->snd_sml = newtp->snd_una =
-        newtp->snd_nxt = newtp->snd_up = treq->snt_isn + 1;
+        seq = treq->snt_isn + 1;
+        newtp->snd_sml = newtp->snd_una = seq;
+        WRITE_ONCE(newtp->snd_nxt, seq);
+        newtp->snd_up = seq;
 
         INIT_LIST_HEAD(&newtp->tsq_node);
         INIT_LIST_HEAD(&newtp->tsorted_sent_queue);